1. Field of the Invention
The described invention relates to the field of imaging. In particular, the invention relates to the selection of an image based on the content of the image.
2. Description of Related Art
Image capture devices, such as still and video cameras, typically have stored images based upon the input of a trigger from the user. Sometimes the trigger is manually input, for example, by pushing a button. The trigger may alternatively be triggered remotely via a coupling to a flash strobe, or through a timer.
Some events, however, are very difficult to trigger upon. As an example, capturing an image of lightning during a lightning storm is very difficult to capture because of the unpredictability of the event, as well as the quick timing that is needed to capture the event.
One way in which lightning could be captured is by taking a video picture of the sky, and hoping that lightning strikes during the time the video is capturing images (the capture period). However, this method fails in several respects.
First, the quality of video is typically not as good as that of a still picture. Second, because the video image must be stored, the capture period is limited to the amount of storage space in the camera. This is restrictive when the target image may take a very long time to happen. Finally, a person has to either be present during the capture period to observe whether lightning had struck to know whether the target image was captured, or the user potentially has to review the entire video to see whether the desired event occurred. A more automated method of detecting a target image is desirable.
An image capture system comprises an image input and processing unit. The image input obtains image information which is then passed to the processing unit. The processing unit determines an image metric from the image information. The processing unit initiates a capture sequence when the image metric meets a predetermined condition. The capture sequence may store one or more images, or it may indicate that one or more images have been detected. In one embodiment, the image input comes from an image sensor, such as a CMOS or CCD sensor. In another embodiment, the image input comes from a video stream.